The present invention provides, among other things, methods and compositions for production of recombinant I2S protein with improved potency and activity using cells co-express I2S and FGE protein. In some embodiments, cells according to the present invention are engineered to simultaneously over-express recombinant I2S and FGE proteins. Cells according to the invention are adaptable to various cell culture conditions. In some embodiments, cells of the present invention adaptable to a large-scale suspension serum-free culture.